1. Technical Field
This invention relates to the field of pipet guns for drawing measured amounts of liquid into a pipet tube, and for dispensing measured amounts, or aliquots, of the liquid from the pipet tube, and more particularly concerns a pipet gun apparatus which is programmable to automatically draw in a desired fill volume of liquid into a pipet tube, and to automatically dispense uniform aliquots of the liquid from the pipet tube, as, for example, to dispense successive aliquots of media to feed growing cells in a number of wells in a tray.
2. Related Inventions
This invention is related to the inventions shown in U.S. Pat. No. 4,624,147 which issued on Nov. 25, 1986; U.S. Pat. No. 3,963,061 which issued on June 15, 1976; and U.S. Pat. No. 3,834,240 which issued on Sept. 10, 1974, all of these patents being issued to Drummond Scientific Company, Broomall, Pa., and all of which are incorporated herein by reference.
3. Background of the Prior Art
The present pipet gun apparatus is an improvement over the prior art in that the pipet guns of the prior art are manually operated, or are electrically operated with wires connected to the pipet gun that restrict its flexibility of use and may cause electrical problems. In manual operation, the operator fills the pipet tube manually by pressing an up valve button on the pipet gun to create a suction and draw the liquid into the pipet tube to a desired fill volume which he judges by eye as he watches the liquid rising in the pipet tube which is calibrated with volume markings. Then he takes the pipet gun and the filled pipet tube to a position over a tray of wells containing cells which are to be fed with the liquid, and he then manually depresses the down valve button to insert desired aliquots of liquid into the wells, and he gauges the volume of each aliquot by eye as he watches the top surface of the liquid recede in the pipet tube as the liquid is being dispensed.
It has long been desired to automatically fill the pipet tube to a desired fill volume, and to automatically dispense desired aliquots of uniform volume, so that the operator does not have to concentrate on filling the pipet tube to a desired calibration line which he must judge by eye, and then dispense desired uniform aliquots by watching the top surface of the liquid in the pipet tube as it lowers to successive calibration lines.
Performing this operation manually by eye can become very tedious and can lead to mistakes, especially if the operator is doing this all day.
Various proposals have been made as to how to solve this problem and how to make the procedure of filling and dispensing automatic. Some of these proposals have included an electrical control unit which is connected by electrical wires or cable to the pipet gun, and which is provided with an electronic key pad for selecting a pipet operating mode from several such modes pre-programmed into the control unit, and for entering certain information, e.g., as to the desired fill volume and the desired volume of the aliquots to be dispensed. However, such systems require the use of electrical wires between the control unit and the pipet gun and these wires make the pipet gun less easily moved when reaching to a position for drawing in liquid, and when reaching to another position for dispensing the liquid, as well as creating possible electrical safety problems which might be caused by excessive flexing of the electrical wires as the pipet gun is being used.